Widespread seasonal speed-up of west Antarctic Peninsula glaciers from 2014 to 2021

Mass loss from the Antarctic Ice Sheet is dominated by ice dynamics, where ocean-driven melt leads to un-buttressing and ice flow acceleration. Long-term ice speed change has been measured in Antarctica over the past four decades; however, there are limited observations of short-term seasonal speed variability on the grounded ice sheet. Here we assess seasonal variations in ice flow speed on 105 glaciers on the west Antarctic Peninsula using Sentinel-1 satellite observations spanning 2014 to 2021. We find an average summer speed-up of 12.4 +/- 4.2%, with maximum speed change of up to 22.3 +/- 3.2% on glaciers with the most pronounced seasonality. Our results show that over the six-year study period, glaciers on the west Antarctic Peninsula respond to seasonal forcing in the ice-ocean-atmosphere system, indicating sensitivity to changes in terminus position, surface melt plus rainwater flux, and ocean temperature. Seasonal speed variations must be accounted for when measuring the mass balance and sea level contribution of the Antarctic Peninsula, and studies must establish the future evolution of this previously undocumented signal under climate warming scenarios. Glaciers on the west Antarctic Peninsula flowed on average 12% faster during the summer compared with winter due to a mix of oceanic and atmospheric influences, according to an analysis of remote sensing data from 2014 to 2021.